Notice
that it is difficult (impossible) to realize practically
the conditions for the
application of the MDA in the limit to the CP, in particular, if we introduce
the restrictions \(T=T_c\)  or \(n=n_c\) . In the way to the CP, one has to stop at small but finite
distance from the CP when a huge bump appear : the MDA variations fail because it becomes smaller
or of the order of next derivatives contributions in expansion
(REF ) of the in-compressibility \(\mathcal {K}_T\)  in the
denominator of the fluctuations \(\omega \) , Eq. (REF ), see
Refs. [1]}, [2]}, [3]}.
The derivations of Eqs. (REF ) and (REF )
become invalid on enough small but finite
distances from
the CP because, probably, we use the mean field approach (in particular, the vdWM) as the basis of the QS
perturbation expansion. As shown in Ref. [4]},
in this case the correlation length
of the correlation function, or
the two-body amplitude of scattering in the quasi-particle Landau theory
[5]}, infinitely
diverges
by increasing relatively, in the considered limit to the CP, with respect
to the mean distance between
particles. In this case, the
arguments of validness
for the derivations of Eqs. (REF ) and (REF )
for the fluctuations \(\omega \)  through the derivatives of
the thermodynamic averages (pressure or particle number density)
contradict [1]}, [2]}
with the
background of the
statistical physics for which we should have an opposite tendency such that
the considered relative fluctuations must be
small; see, e.g.,
Refs. [1]}, [2]}, [4]}, [11]}.
